The two most destructive totalitarian states in Europe's recent history -- Bolshevik Soviet Union and Nazi Germany -- cooperated since the 1930s until early summer 1941. The cooperation was sealed through a written agreement in Moscow on 23 August 1939. The agreement is known in history books as the Molotov-Ribbentrop Pact. The two instigators of the Second World War committed war crimes and crimes against humanity on a scale that was unheard of in modern history.